An autonomous vehicle, e.g., an automobile, bus, truck, watercraft, etc., may include a computing device executing instructions for operating the vehicle either wholly or partially autonomously, i.e., without input from a human operator. For example, the vehicle computing device may receive data from one or more sensors, and then process sensor data to provide input to the computing device for determining autonomous operations of the vehicle. Vehicle sensor data may provide a variety of information concerning a road, road conditions, weather conditions, potential obstacles, other vehicles, etc. However, vehicle sensor data does not provide all of the data that may be useful to an autonomous vehicle computing device for autonomously operating the vehicle. For example, vehicle sensor data cannot always be relied upon to provide useful or even vital information about other vehicles, e.g., whether other vehicles are autonomous.